这个有点复杂，按理应该写写的……下次再说吧
#include<iostream> #include<cstdio> #include<algorithm> using namespace std; struct node { int l,r,sum; #define l(x) tr[x].l #define r(x) tr[x].r #define sum(x) tr[x].sum }tr[10000000]; struct que { char a;int l,r,kth; }qq[20010]; int cnt,m,ce,T[20010],S[20010]; int n,Q,a[20010],b[20010]; int use[3][20010]; inline int lowbit(int x){return x&(-x);} inline int build(int l,int r) { int now=++cnt; if(l==r)return now; int mid=(l+r)>>1; l(now)=build(l,mid); r(now)=build(mid+1,r); return now; } inline int build_new(int flag,int mark,int loc,int val) { int rt=++cnt; int before; if(mark==1)before=T[0]; else before=flag?T[mark-1]:S[mark-1]; if(!flag && val) before=S[mark]; sum(rt)=sum(before)+val; int l=1,r=m,now=rt,still=before,mid; for(;l(still)||r(still);) { mid=(l+r)>>1; if(loc>mid) { l(now)=l(still);r(now)=++cnt; sum(cnt)=sum(r(still))+val; now=cnt;still=r(still); l=mid+1; } else { r(now)=r(still);l(now)=++cnt; sum(cnt)=sum(l(still))+val; now=cnt;still=l(still); r=mid; } } return rt; } inline void updata(int loc,int num) { int where; where=lower_bound(b+1,b+m+1,a[loc])-b; for(int i=loc;i<=n;i+=lowbit(i)) S[i]=build_new(0,i,where,-1); where=lower_bound(b+1,b+m+1,num)-b; for(int i=loc;i<=n;i+=lowbit(i)) S[i]=build_new(0,i,where,1); a[loc]=num; } int Sum(int y,int x) { int res=0; for(int i=x;i>=1;i-=lowbit(i)) res+=sum(l(use[y][i])); return res; } int ask(int u,int v,int a,int b,int l,int r,int k) { if(l==r)return l; int lm=Sum(2,v)+sum(l(b))-sum(l(a))-Sum(1,u), mid=(l+r)>>1; if(k<=lm) { for(int i=u;i>=1;i-=lowbit(i)) use[1][i]=l(use[1][i]); for(int i=v;i>=1;i-=lowbit(i)) use[2][i]=l(use[2][i]); return ask(u,v,l(a),l(b),l,mid,k); } else { for(int i=u;i>=1;i-=lowbit(i)) use[1][i]=r(use[1][i]); for(int i=v;i>=1;i-=lowbit(i)) use[2][i]=r(use[2][i]); return ask(u,v,r(a),r(b),mid+1,r,k-lm); } } signed main() { cin>>n>>Q;ce=n; for(int i=1;i<=n;i++)cin>>a[i],b[i]=a[i]; for(int i=1;i<=Q;i++) { cin>>qq[i].a>>qq[i].l>>qq[i].r; if(qq[i].a=='Q')cin>>qq[i].kth; else b[++ce]=qq[i].r; } sort(b+1,b+ce+1); m=unique(b+1,b+ce+1)-b-1; T[0]=build(1,m); for(int i=1;i<=n;i++) { int loc=lower_bound(b+1,b+m+1,a[i])-b; T[i]=build_new(1,i,loc,1); } for(int i=1;i<=n;i++) S[i]=build_new(0,i,1,0); for(int i=1;i<=Q;i++) { if(qq[i].a=='Q') { int x=qq[i].l,y=qq[i].r; for(int j=x-1;j>=1;j-=lowbit(j)) use[1][j]=S[j]; for(int j=y;j>=1;j-=lowbit(j)) use[2][j]=S[j]; printf("%ld\n",b[ask(x-1,y,T[x-1],T[y],1,m,qq[i].kth)]); } else updata(qq[i].l,qq[i].r); } }